Medical treatment often requires the administration of a therapeutic agent (e.g., medicament, drugs, etc.) to a particular part of a patient's body. As patients live longer and are diagnosed with chronic and/or debilitating ailments, the likely result will be an increased need to place even more protein therapeutics, small-molecule drugs, and other medications into targeted areas throughout the patient's body. Some maladies, however, are difficult to treat with currently available therapies and/or require administration of drugs to anatomical regions to which access is difficult to achieve.
A patient's eye is a prime example of a difficult-to-reach anatomical region, and many vision-threatening diseases, including retinitis pigmentosa, age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma, are difficult to treat with many of the currently available therapies. For example, oral medications can have systemic side effects; topical applications may sting and engender poor patient compliance; injections generally require a medical visit, can be painful, and risk infection; and sustained-release implants must typically be removed after their supply is exhausted (and generally offer limited ability to change the dose in response to the clinical picture).
Another example is cancer, such as breast cancer or meningiomas, where large doses of highly toxic chemotherapies, such as rapamycin, bevacizumab (e.g., AVASTIN), or irinotecan (CPT-11), are typically administered to the patient intravenously, which may result in numerous undesired side effects outside the targeted area. Yet another example is drug delivery to the knee, where drugs often have difficulty penetrating the avascular cartilage tissue for diseases such as osteoarthritis.
Implantable drug-delivery devices, which may have a refillable drug reservoir, a cannula for delivering the drug, etc., generally allow for controlled delivery of pharmaceutical solutions to a specified target. As drug within the drug reservoir depletes, the physician can refill the reservoir with, for example, a syringe, while leaving the device implanted within the patient's body. This approach can minimize the surgical incision needed for implantation and typically avoids future or repeated invasive surgery or procedures.
A variety of challenges, however, are associated with refillable drug-delivery devices. For example, while a fill port may be located on a surface of the device to facilitate post-implantation access, the fact that the device is installed within the patient's anatomy may make such access uncomfortable for the patient and risk damage to the device. Such difficulties are especially problematic if the device is refilled manually. When filling the drug reservoir using a handheld syringe, for example, it is possible to generate large pressures in the syringe, particularly when small volumes are involved and the syringe plunger is of small diameter. These high pressures may damage the device and/or cause improper drug expulsion. Also, trying to refill the drug-delivery device with a handheld single-barrel syringe can require several cycles of needle insertion and withdrawal as different fluids are removed and injected into the device. This may cause stress for both the patient and the doctor, and creates unnecessary wear on the fill port.
A need exists, therefore, for improved implantable drug-delivery devices, and apparatus and methods for filling such devices.